Catalyst and methods for olefin acetoxylation

Abstract

Disclosed herein catalyst, a catalyst substrate, a catalyst and catalyst substrate shape, and a process of acetoxylating olefins using the same. The catalyst can comprise a support material having a catalytic layer disposed thereon and having a pimpled and/or dimpled shape as defined herein. The catalytic layer can comprise palladium and gold.

What is claimed is: 
     
         1 . A catalyst for the acetoxylation of olefins, comprising:
 a support material having a pimpled external surface; and   a catalytic layer disposed on the external surface, wherein the catalytic layer comprises palladium and gold.   
     
     
         2 . The catalyst according to  claim 1 , wherein the support material is a pimpled sphere. 
     
     
         3 . The catalyst according to  claim 2 , wherein the support material has a diameter from 4 mm to 8 mm, as measured from the longest diameter of the sphere excluding the pimples. 
     
     
         4 . The catalyst according to  claim 1 , wherein the diameter of the pimples, if the pimples were full spheres, is from 0.5 mm to 8 mm. 
     
     
         5 . The catalyst according to  claim 2 , wherein the diameter of the pimples, if the pimples were full spheres, is from 10% to 75% of the diameter of the sphere of the support material without the pimples. 
     
     
         6 . The catalyst according to  claim 1 , wherein the pimples of the support material have a length from their center, if the pimple were a full sphere, to the center of the sphere of the catalyst support material of from 0.1 mm to 5 mm. 
     
     
         7 . The catalyst according to  claim 1 , wherein the support material comprises silica. 
     
     
         8 . The catalyst according to  claim 7 , wherein the support material further comprises alumina. 
     
     
         9 . The catalyst according to  claim 8 , wherein the support material comprises from 60 to 99 wt. % silica and from 1 to 40 wt. % alumina. 
     
     
         10 . The catalyst according to  claim 1 , wherein the catalyst has a void fraction in a 250 mL graduated cylinder (38 mm diameter) of 0.41 or greater. 
     
     
         11 . The catalyst according to  claim 1 , wherein the catalyst layer has a thickness from 100 to 300 μm. 
     
     
         12 . The catalyst according to  claim 1 , wherein the catalytic layer has an average penetration depth into the support material from 115 to 175 microns. 
     
     
         13 . The catalyst according to  claim 1 , wherein the weight ratio of palladium to gold is ≤2:1 
     
     
         14 . The catalyst according to  claim 1 , wherein the weight ratio of palladium to gold is from 1.6:1 to 2:1. 
     
     
         15 . The catalyst according to  claim 1 , wherein the catalyst comprises from 7 to 10 g/L palladium and from 3 to 8 g/L gold. 
     
     
         16 . A process for the acetoxylation of an olefin in a gaseous reaction stream containing an olefin, acetic acid, and an oxygen-containing gas, the process comprising:
 passing a reaction gas over a reaction tube comprising a catalyst to form an acetoxylated olefin;
 wherein the catalyst comprises a support material having a pimpled external surface, and 
 a catalytic layer disposed on the external surface, wherein the catalytic layer comprises palladium and gold. 
   
     
     
         17 . The process of  claim 16 , wherein the olefin is ethylene and wherein the selectivity to vinyl acetate monomer is at least 60%. 
     
     
         18 . The process of  claim 16 , wherein the olefin is ethylene and wherein the overall process conversion of ethylene is at least 60%. 
     
     
         19 . The process of any of  claim 16 , wherein the olefin is ethylene and the oxygen conversion is from 35 to 55%. 
     
     
         20 . The process of any of  claim 16 , wherein the olefin is ethylene and the selectivity to carbon dioxide is less than 10%. 
     
     
         21 . The process of any of  claim 16 , wherein the olefin is ethylene and the STY is at least 800 g vinyl acetate monomer/L/hour. 
     
     
         22 . The process of any of  claim 16 , wherein the temperature across the reaction tube is from 145 to 205° C.